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Very low compression, what to look for?

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G-Man
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Post by G-Man » Sat Aug 16, 2014 12:19 am

The oil may be leaking further up and running down to that point. Tightening the exhaust flange won't help.

G
'60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160
'66 Matchless 350 '67 CL77
'67 S90 '77 CB400F

deafanddiabetic
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Post by deafanddiabetic » Sat Aug 16, 2014 12:29 am

So more likely a bad gasket/leaking gasket or exhaust valve not seating correctly?
G-Man wrote:The oil may be leaking further up and running down to that point. Tightening the exhaust flange won't help.

G

deafanddiabetic
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Post by deafanddiabetic » Wed Sep 03, 2014 3:25 pm

Well, more adventures to this story.

I realized that I had bought standard sized rings for .5 O/S pistons, so I took the engine apart to replace those.

Now that everything is back together again and adjusted, I'm dry firing about 100psi per cylinder after 5 kicks. I have not put the engine into the bike yet, but my local mechanic said that it'll probably be a little while before the rings seat into the cylinders and my compression will go up.

Man, this has been a headache.

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G-Man
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Post by G-Man » Fri Sep 05, 2014 5:49 am

The headache is just the result of all that knowledge being stored....... :-)

G
'60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160
'66 Matchless 350 '67 CL77
'67 S90 '77 CB400F

deafanddiabetic
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Post by deafanddiabetic » Mon Sep 15, 2014 2:28 pm

https://www.facebook.com/video.php?v=10 ... 2276431180

In that link is a video of it running now. I put in proper piston rings, ordered another gasket set, installed O-Rings on the two posts on the cylinder base and put new O-Rings into the tappet covers. I torqued the head to 18ft/lbs last time according to my manual. I did it to 20ft/lbs this time.

It's literally pouring out of somewhere that looks higher than the head gasket. I have no idea what to do, I'm getting pretty bummed out about this project.

Someone suggested that I might have a hairline crack in the head?

deafanddiabetic
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Joined: Thu Jun 19, 2014 6:04 pm
Location: Nebraska

Post by deafanddiabetic » Mon Sep 15, 2014 2:30 pm

Just to clarify, I do know that the header flange is broken, I snapped it today. It leaked from the same place before I took the engine apart again. When I told my mechanic that it was leaking from the exhaust port he thought I was crazy, hah.

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G-Man
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Post by G-Man » Mon Sep 15, 2014 2:33 pm

The video doesn't work for me.

G
'60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160
'66 Matchless 350 '67 CL77
'67 S90 '77 CB400F

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